This invention relates to a novel spinal needle assembly.
Typical spinal needle assemblies comprise an obturator having an end cap, a cannula having a needle bevel at one end and a hub at the opposite end, and a housing for the obturator and the cannula. The obturator extends into the cannula so that the end of the obturator opposite its end cap is substantially aligned with the bevel at the one end of the cannula, so as to prevent coring during insertion of the spinal needle.
Prior to or during insertion of the spinal needle, occasionally the obturator will become disengaged from the cannula. This problem is particularly serious with smaller diameter gauges, when the unit is inverted by the operator. Such disengagement or backoff of the obturator from the cannula is a serious problem and can create the environment for potential tissue traps which can later be deposited within the subarachnoid space, possibly resulting in the formation of epidermoid tumors.
Typically, the spinal needle assembly utilizes a cap dink, which serves to align the obturator cap with the cannula hub. However, it has been found that this cap dink does not necessarily maintain the cap and hub in proper aligned relationship, particularly when the spinal needle assembly is inverted or tilted drastically prior to insertion.
It is, therefore, an object of the present invention to provide means for maintaining the obturator within the lumen of its mated cannula. However, it is important that the operator have the ability to remove the obturator quickly and smoothly. Thus, any means for maintaining the obturator within the cannula must be easy to remove and must enable simple, smooth and rapid removal of the obturator with respect to the cannula.
Further, while the typical spinal needle assembly has utilized a hub slot and cap dink for aligning the cap and hub, the slot/dink relationship is designed as a bevel match locator, and is not intended to be an obturator locking device.
We have discovered a system by which the obturator and the cannula can be effectively locked in place and properly aligned during insertion, yet the obturator can be pulled rapidly and smoothly from the cannula once insertion has been effected.
It is, therefore, an object of the present invention to provide a spinal needle assembly having obturator backoff prevention means.
Another object of the present invention is to provide a spinal needle assembly in which the obturator can be removed quickly and smoothly.
Other objects and advantages of the present invention will become apparent as the description proceeds.